EP1979153B1 - Apparatus for blow moulding containers, comprising transport elements with two gripper arms - Google Patents

Abstract

The apparatus serves for blow molding containers. Preforms of a thermoplastic material are heated in the region of a heating zone and subsequently transferred to a blow molding device. The blow molding device is provided with at least one blow molding station for transforming the preforms into the containers. Provided for handling the preforms is a gripper-like transporting element (41) with two gripper arms (45, 46), which are arranged pivotably in relation to a gripper carrier (42). Each of the gripper arms can be pivoted by means of at least one lever and is coupled with a central element (49). The central element is arranged at least partly between the gripper arms. Each of the gripper arms is resiliently clamped with respect to the central element by at least one spring (56, 57).

Description

The invention relates to a device for blow-molding of containers, which has a heating section for heating preforms of a thermoplastic material and which is provided with a blowing device having at least one blowing station for forming the preforms in the container, as well as in the handling of the preforms at least one pincer-like transport element is provided with two pincer arms, which are arranged pivotable relative to a pincer carrier.

In a container molding by blowing pressure preforms of a thermoplastic material, such as preforms made of PET (polyethylene terephthalate), supplied to different processing stations within a blow molding machine. Such a blow molding machine typically has a heating device and a blowing device, in the region of which the previously tempered preform has a biaxial orientation is expanded to a container. The expansion takes place with the aid of compressed air, which is introduced into the preform to be expanded. The procedural sequence in such an expansion of the preform is in the DE-OS 43 40 291 explained. The introductory mentioned introduction of the pressurized gas also includes the introduction of compressed gas into the developing container bubble and the introduction of compressed gas into the preform at the beginning of the blowing process.

The basic structure of a blowing station for container molding is in the DE-OS 42 12 583 described. Possibilities for tempering the preforms are in the DE-OS 23 52 926 explained.

Within the blow molding apparatus, the preforms as well as the blown containers can be transported by means of different handling devices. It is known to use transport spikes on which the preforms are plugged. The preforms can also be handled with other support devices. The use of grippers for handling preforms and the use of clamping mandrels which can be inserted for mounting in a mouth region of the preform are also among the available constructions.

Handling of containers and preforms using transfer wheels, for example, in the DE-OS 199 06 438 in an arrangement of a transfer wheel between a blowing wheel and an output path and a further transfer gear between the heating path and the blowing wheel described.

The already described handling of the preforms takes place firstly in the so-called two-stage process, in which the preforms are first produced in an injection molding process, then temporarily stored and later conditioned with respect to their temperature and inflated to a container. on the other hand, it is used in the so-called one-step process, in which the preforms are suitably tempered and then inflated immediately after their injection molding production and adequate solidification.

With regard to the blow molding stations used, different embodiments are known. In blow molding stations which are arranged on rotating transport wheels, a book-like unfoldability of the mold carriers is frequently encountered. But it is also possible to use relatively movable or differently guided mold carrier. In fixed blowing stations, which are particularly suitable for receiving a plurality of cavities for container molding, typically plates arranged parallel to one another are used as mold carriers.

The use of forceps for handling the preforms can be done both exclusively and in combination with other support or handling elements. For example, the preforms can be supported by transport spikes along a part of their transport path, and along at least one further part of the transport path, handling using pliers is possible. However, the pliers used so far can not yet meet all the requirements that are placed on a gentle yet reliable handling of the preforms.

The essential requirements are a reliable and trouble-free handling of the preforms at high production rates of preforms per unit time. Conveniently, the pliers should be suitable both for handling preforms and for handling blown bottles. In addition, mechanical damage to the preforms as a result of handling by the pliers should be avoided or minimized.

From the WO 03 / 099688A already a device for blow molding is known, are applied to the preforms and containers using pliers-like transport elements. The transport elements each have two gun arms, which are arranged pivotable relative to a clamp carrier.

In the EP-A-1 375 395 Also, a pliers-like transport element for bottles is described which has two pliers arms which are arranged pivotable relative to a pliers carrier. In a closed state of the pliers, the closed positioning is stabilized by two interacting permanent magnets, so that it is not necessary to apply external holding forces. In a fully open state, lever pliers arms are in an over-center position, so that here, too, no external forces for maintaining the state are required. A force is thus required only in a state change of the pliers.

Object of the present invention is to construct a device of the aforementioned type such that a reliable transport of the preforms is supported at high transport speed.

This object is achieved in that each of the pliers arms via at least one lever is pivotally coupled to a central element, which is at least partially disposed between the gun arms and that each of the pliers arms is resiliently clamped by at least one spring against the central element and that the central element movably guided relative to the gun carrier.

The arrangement of the central element between the forceps arms enables automatic closing of the forceps arms directly by inserting the preform between the forceps arms and a resulting pressure on the central element. It is also possible in a simple manner to position the central element for a release of the preforms and thereby perform both a Aufschwenkbewegung the gun arms and an output of the preforms. The above and below listed handling of the preforms using the pliers arms also applies to the handling of blown containers in the same way, without being separately referred to each time. Due to the resilient tension of the gun arms relative to the central element, an automatic support of the preforms or bottles is supported without the use of separate locks or active actuators.

A simple movement coupling is supported by the fact that the levers are arranged obliquely to a central longitudinal axis of the central element.

In particular, it is envisaged that the levers are arranged in a direction away from the clamp carrier obliquely forward facing.

To stabilize predetermined positions of the gun arms, it helps that the springs are arranged with spring longitudinal axes obliquely to the central longitudinal axis.

It proves to be particularly advantageous that the spring longitudinal axes are arranged obliquely forwards in a direction away from the clamp carrier.

A compact construction is supported by the fact that the central element is movably guided relative to the clamp carrier.

A high mechanical stability in a closed state can be achieved in that the central element in a lateral region has a step-shaped contour and that the pliers arms to the contour having the central element adapted outer contour.

Gentle handling of the preforms is assisted by the fact that the forceps arms have, in the region of their extension facing away from the forceps carrier, a holding contour matched to the preform.

It also contributes to a simple controllability and to a gentle handling of the preforms that the central element in the region of its extension facing away from the pliers carrier has a contact surface adapted to the outer geometry of the preform.

An external controllability of the transport element is provided by the fact that the central element has a matched to a cam control customer.

A simple mechanical construction is supported by the fact that the cam control is designed exclusively for specifying an opening movement of the transport element.

A state stabilization in a mounting position of the transport element is achieved in that the spring longitudinal axis is arranged in a closed state of the transport element obliquely to the longitudinal axis lever that the spring longitudinal axis extends at least partially between the longitudinal axis of the lever and the central longitudinal axis.

A further state stabilization in an opening positioning of the transport element is achieved in that the spring longitudinal axis in an open state the transport element extends at least partially relative to the central longitudinal axis on the outside next to the lever longitudinal axis.

Fig. 1

Eine perspektivische Darstellung einer Blassta- tion zur Herstellung von Behältern aus Vorform- lingen,

Fig. 2

einen Längsschnitt durch eine Blasform, in der ein Vorformling gereckt und expandiert wird,

Fig. 3

eine Skizze zur Veranschaulichung eines grund- sätzlichen Aufbaus einer Vorrichtung zur Blas- formung von Behältern,

Fig. 4

eine modifizierte Heizstrecke mit vergrößerter Heizkapazität,

Fig. 5

eine perspektivische Darstellung eines Trans- portelementes mit zwei Zangenarmen und einem Zentralelement in einem geschlossenen Zustand der Zange,

Fig. 6

die Anordnung gemäß Fig. 5 nach einem Öffnen der Zange,

Fig. 7

die Anordnung gemäß Fig. 5 in einer Draufsicht,

Fig. 8

die Anordnung gemäß Fig. 6 in einer Draufsicht.

In the drawings, embodiments of the invention are shown schematically. Show it:

Fig. 1

A perspective view of a blowing station for the production of containers from preforms,

Fig. 2

a longitudinal section through a blow mold, in which a preform is stretched and expanded,

Fig. 3

a sketch to illustrate a basic structure of a device for blow molding containers,

Fig. 4

a modified heating section with increased heating capacity,

Fig. 5

a perspective view of a transport element with two gun arms and a central element in a closed state of the pliers,

Fig. 6

the arrangement according to Fig. 5 after opening the pliers,

Fig. 7

the arrangement according to Fig. 5 in a plan view,

Fig. 8

the arrangement according to Fig. 6 in a top view.

The basic structure of a device for forming preforms (1) in container (2) is in Fig. 1 and in Fig. 2 shown. The arrangement can be as shown or rotated in a vertical plane by 180 °.

The device for forming the container (2) consists essentially of a blowing station (3), which is provided with a blow mold (4) into which a preform (1) can be inserted. The preform (1) may be an injection-molded part of polyethylene terephthalate. To allow the preform (1) to be inserted into the blow mold (4) and to allow the finished container (2) to be removed, the blow mold (4) consists of mold halves (5, 6) and a bottom part (7), which is a lifting device (8) is positionable. The preform (1) can be fixed in the region of the blowing station (3) by a retaining element (9). It is for example possible to use the preform (1) via pliers or other handling means directly into the blow mold (4).

To allow a compressed air supply line below the blow mold (4), a connecting piston (10) is arranged, which supplies compressed air to the preform (1) and at the same time performs a seal. In a modified construction, it is basically also conceivable to use solid compressed air supply lines.

A stretching of the preform (1) takes place in this embodiment by means of a stretching rod (11), which is positioned by a cylinder (12). According to another embodiment, a mechanical positioning of the stretch rod (11) is carried out over curve segments, which are acted upon by Abgriff rollers. The use of curve segments is particularly useful when a plurality of blowing stations (3) on a rotating blowing wheel (25) are arranged

At the in Fig. 1 In the embodiment shown, the stretching system is designed such that a tandem arrangement of two cylinders (12) is provided. From a primary cylinder (13), the stretch rod (11) is first moved to the area of a bottom (14) of the preform (1) before the beginning of the actual stretching operation. During the actual stretching process, the primary cylinder (13) with extended stretching rod together with a carriage (15) carrying the primary cylinder (13) is positioned by a secondary cylinder (16) or via a cam control. In particular, it is envisaged to use the secondary cylinder (16) in such a cam-controlled manner that a current stretching position is predetermined by a guide roller (17) which slides along a curved path during the execution of the stretching operation. The guide roller (17) is pressed by the secondary cylinder (16) against the guideway. The carriage (15) slides along two guide elements (18).

After closing the mold halves (5, 6) arranged in the region of carriers (19, 20), the carriers (19, 20) are locked relative to one another by means of a locking device (20).

To adapt to different shapes of a mouth portion (21) of the preform (1) is according to Fig. 2 the use of separate threaded inserts (22) in the area of the blow mold (4) provided.

Fig. 2 shows in addition to the blown container (2) and dashed lines drawn the preform (1) and schematically a developing container bladder (23).

Fig. 3 shows the basic structure of a blow molding machine, which is provided with a heating section (24) and a rotating blowing wheel (25). Starting from a preform input (26), the preforms (1) are transported by transfer wheels (27, 28, 29) into the region of the heating path (24). Heater (30) and fan (31) are arranged along the heating path (24) in order to temper the preforms (1). After a sufficient temperature control of the preforms (1), they are transferred to the blowing wheel (25), in the region of which the blowing stations (3) are arranged. The finished blown containers (2) are fed by transfer wheels (37, 28, 38) to a delivery line (32).

In order to be able to transform a preform (1) into a container (2) in such a way that the container (2) has material properties which ensure a long useful life of foodstuffs filled inside the container (2), in particular drinks, special process steps must be taken the heating and orientation of the preforms (1) are maintained. In addition, advantageous effects can be achieved by adhering to special dimensioning regulations.

As a thermoplastic material different plastics can be used. For example, PET, PEN or PP can be used.

The expansion of the preform (1) during the orientation process is carried out by compressed air supply. The Compressed air supply is in a Vorblasphase in which gas, for example, compressed air, is supplied at a low pressure level and divided into a subsequent Hauptblasphase in which gas is supplied at a higher pressure level. During the pre-blowing phase, compressed air is typically used at a pressure in the interval of 10 bar to 25 bar and during the main blowing phase compressed air is supplied at a pressure in the interval of 25 bar to 40 bar.

Out Fig. 3 is also recognizable that in the illustrated embodiment, the heating section (24) is formed of a plurality of revolving transport elements (33) which are strung together like a chain and guided by guide wheels (34). In particular, it is envisaged that the chain-like arrangement will open up a substantially rectangular basic contour. In the illustrated embodiment, in the region of the transfer wheel (27) facing extension of the heating section (24), a single relatively large-sized guide wheel (34) and in the region of adjacent deflections two comparatively smaller dimensioned guide wheels (36) used. In principle, however, any other guides are conceivable.

To enable a possible dense arrangement of the transfer wheel (27) and the blowing wheel (25) relative to each other, the arrangement shown to be particularly useful, since in the region of the corresponding extent of the heating section (24) three deflecting wheels (34, 36) are positioned, and Although in each case the smaller deflection wheels (36) in the region of the transition to the linear curves of the heating section (24) and the larger deflection (34) in the immediate transfer area to the transfer wheel (27) and the blowing wheel (25). Alternative to Using chain-like transport elements (33), it is also possible, for example, to use a rotating heating wheel.

After a finished blowing of the containers (2), they are led out of the region of the blowing stations (3) by the transfer wheel (38) and transported to the delivery line (32).

In the in Fig. 4 shown modified Heizstrekke (24) can be tempered by the larger number of radiant heaters (30) a larger amount of preforms (1) per unit time. The fans (31) introduce cooling air into the region of cooling air ducts (39), which in each case oppose the associated radiant heaters (30) and emit the cooling air via outflow openings. By arranging the outflow directions, a flow direction for the cooling air is realized substantially transversely to a transport direction of the preforms (1). The cooling air ducts (39) can provide reflectors for the heating radiation in the area opposite the radiant heaters (30), and it is likewise possible to realize cooling of the radiant heaters (30) via the discharged cooling air.

A transport of the preforms (1) and the container (2) by the blow molding machine can be done in different ways. According to one embodiment variant, the preforms are carried by transport spikes at least along the essential part of their transport path. But it is also possible to carry out a transport of the preforms using forceps, which attack the outside of the preform, or to use inner mandrels, which in a mouth region of the Preform are introduced. Likewise, different variants are conceivable with regard to the spatial orientation of the preforms.

According to a variant of the preform in the preform input (26) is fed with its mouth oriented vertically upwards, then rotated, along the heating section (24) and the blowing wheel (25) oriented with its mouth in the vertical direction down and promoted turned again before reaching the output section (32). According to another variant, the preform (2) in the region of the heating section (24) with its mouth in the vertical direction is heated oriented downwards, but rotated again by 180 ° before reaching the blowing wheel (25).

According to a third embodiment, the preform passes through the entire area of the blow molding machine without performing turning operations with its mouth oriented in a vertical direction upwards.

Fig. 5 shows in a perspective view of a pincer-like transport element (41) content Erten preform (1). In a similar manner, the transport element (41) can also position a blown container (2). The transport element (41) has a forceps carrier (42) which is connected via pivot joints (43, 44) with forceps arms (45, 46). The pliers arms (45, 46) are coupled via levers (47, 48) with a central element (49). The levers (47, 48) are connected by pivot joints (50, 51) with the tong arms (45, 46) and pivot joints (52, 53) with the central element (49). The central element (49) has a recess (54) into which a with the clamp carrier (42) connected holding element (55) is inserted. According to an alternative embodiment, the holding element (55) with the central element (49) may also be integrally connected.

At least one of the pivot joints (43, 44, 50, 51, 52, 53) can be realized as a pin-recess combination, hinge, film hinge or solid-state joint. When using film joints or solid joints, it is possible to form all components of the transport element (41) with the exception of the springs (56, 57) in one piece or to combine some of the components into one or more modules.

The pliers arms (45, 46) are additionally connected by springs (56, 57) to the holding element (55). Preferably, the springs (56, 57) are formed as tension springs and in the region of their holding element (55) facing away from extension of pins (58, 59) supported, which are arranged as an extension of the pivot joints (50, 51).

Fig. 5 shows the transport element (41) in a closed state, in which the preform (1) by the gun arms (45, 46) is supported. By the springs (55, 57), the gun arms (45, 46) and the central element (49) are stabilized in the illustrated closed position. It can be seen in particular that both the levers (47, 48) with lever longitudinal axes (60, 61) and the springs (56, 57) with spring longitudinal axes (62, 63) obliquely to a central longitudinal axis (64) of the central element (49). are arranged. The lever longitudinal axes (60, 61) and the spring longitudinal axes (62, 63) in this case extend with respect to the central longitudinal axis (64) in Direction to the preform (1) pointing diagonally forward.

At the in Fig. 5 The central longitudinal axis (64) is in this case between the gun arms (45, 46) arranged and the pliers arms (45, 46) lie in the illustrated closed position laterally on the central element ( 49).

Fig. 6 shows the arrangement according to Fig. 5 after performing an opening movement of the gun arms (45, 46). According to the embodiment shown here, the holding element (55) is rigidly connected to the central element (49) and is displaced together with the central element (49) relative to the forceps carrier (45). The shift can be done for example by an external cam control. By the positioning movement of the central element (49), the levers (47, 48) and thus also the pliers arms (45, 46) are pivoted and release the preform (1).

Fig. 7 shows to further illustrate the principle of operation, the arrangement according to Fig. 5 in a top view. It can be seen in particular that the longitudinal axes of the levers (60, 61) and the spring longitudinal axes (62, 63) are arranged at an angle to each other. The springs (56, 57) thereby pull the pliers arms (45, 46) against the central element (49) and lead to a mounting of the preform (1) by the transport element (41). The levers (47, 48) are in the illustrated positioning in an over-center position, so that caused by the spring force displacement of the central element (49) in the direction of the central longitudinal axis (64) the locking state of the transport element (41) stabilized.

Fig. 8 shows the arrangement according to Fig. 7 after opening the transport element (41) to carry out a release of the preform (1). The central element (49) has been displaced by an external actuating force in the direction of the central longitudinal axis (64) and due to the coupling via the levers (47, 48) causes an opening of the tong arms (45, 46). In the illustrated positioning, the lever longitudinal axes (60, 61) and the spring longitudinal axes (62, 63) are in turn arranged obliquely relative to each other. With respect to the levers (47, 48), however, the skewing takes place in relation to the positioning in Fig. 7 on a respective opposite side of the lever (47, 48). Due to the in Fig. 8 illustrated arrangement of the longitudinal axes of the levers (60, 61) and the spring longitudinal axes (62, 63), the force of the springs (56, 57) to stabilize the illustrated opening position, so that even this state is maintained without external forces.

The illustrated in the figures construction of the transport element (61) thus leads to an extremely simple control of the transport element (41). Starting from the illustration in Fig. 8 If an input of the preform (1) a closing movement in a simple manner by a direct pressure contact of the preform (1) on a pressure surface (65) of the central element (49) can be specified. The contour of the pressure surface (65) is preferably adapted to an outer contour of the preform (1) in the intended pressure range. Relative movements between the preform (1) and the pressure surface (65) can be avoided. With a very low force, the preform can (1) move the central element (49) slightly in the direction of the forceps support (42) and a final closing movement takes place due to the force of the springs (56, 58). As an alternative to an immediate adjustment by the preform (1) or the blown container (2), of course, a positioning of the central element (49) by a cam control or other suitable positioning can be done.

A transfer of the transport element (41) from the closed state according to Fig. 7 in the opening state according to Fig. 8 can also be done again with little effort, since only the first part of the opening movement must be controlled after exceeding an overlap of the lever longitudinal axes (60, 61) and the spring longitudinal axes (62, 63) termination of the opening movement by the force of the springs (56, 57).

The transport element (41) makes it possible to carry out symmetrical opening thoughts / closing movements and avoids friction effects on the preform (1).

Claims (12)

1. Apparatus for blow moulding containers (2), which has a heating section (24) for heating preforms (1) of a thermoplastic material and which is provided with a blowing device which has at least one blowing station (3) for reshaping the preforms (1) into the containers (2), and in which at least one gripper-like transport element (41) having two gripper arms (45, 46), which are arranged pivotably relative to a gripper carrier (42), is provided for handling the preforms (1), characterised in that each of the gripper arms (45, 46) is pivotably coupled to a central element (49) by way of at least one lever (47, 48) in each case, which central element is arranged at least partially between the gripper arms (45, 46), and in that each of the gripper arms (45, 46) is braced resiliently with respect to the central element (49) by at least one spring and in that the central element (49) is movably guided relative to the gripper carrier (42).
2. Apparatus according to Claim 1, characterised in that the levers (47, 48) are arranged at an angle to a central longitudinal axis (64) of the central element (49).
3. Apparatus according to Claim 1 or 2, characterised in that the levers (47, 48) are arranged such that they point forwards at an angle in a direction away from the gripper carrier (42).
4. Apparatus according to one of Claims 1 to 3, characterised in that the springs (56, 57) are arranged with spring longitudinal axes (62, 63) at an angle to the central longitudinal axis (64).
5. Apparatus according to one of Claims 1 to 4, characterised in that the spring longitudinal axes (62, 63) are arranged such that they point forwards at an angle in a direction away from the gripper carrier (42).
6. Apparatus according to one of Claims 1 to 5, characterised in that the central element (49) has a step-shaped contour in a lateral region and in that the gripper arms (45, 46) have an outer contour adapted to the contour of the central element (49).
7. Apparatus according to one of Claims 1 to 6, characterised in that the gripper arms (45, 46) have a holding contour adapted to the preform (1) in the region of their extent away from the gripper carrier.
8. Apparatus according to one of Claims 1 to 7, characterised in that the central element (49) has a pressure face (65) adapted to the outer geometry of the preform (1) in the region of its extent away from the gripper carrier (42).
9. Apparatus according to one of Claims 1 to 8, characterised in that the central element (49) has a consumer adapted to a cam control.
10. Apparatus according to one of Claims 1 to 9, characterised in that the cam control is designed exclusively for specifying an opening movement of the transport element (41).
11. Apparatus according to one of Claims 1 to 10, characterised in that, in a closed state of the transport element (41), the spring longitudinal axis (62, 63) is arranged at an angle to the lever longitudinal axis (60, 61) in such a way that the spring longitudinal axis (62, 63) extends at least partially between the lever longitudinal axis (60, 61) and the central longitudinal axis (64).
12. Apparatus according to one of Claims 1 to 11, characterised in that, in an open state of the transport element (41), the spring longitudinal axis (62, 63) extends at least partially on the outer side relative to the central longitudinal axis (64), near to the lever longitudinal axis (60, 61).

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